The present invention is directed to a solderless connector with multiple modes of compliance and to a replaceable chip module utilizing the present connector for electrically connecting one or more first circuit members to a second circuit member.
The current trend in connector design for those connectors utilized in the computer field is to provide both high density and high reliability connectors between various circuit devices. High reliability for such connections is essential due to potential system failure caused by improper connections of devices. Further, to assure effective repair, upgrade, testing and/or replacement of various components, such as connectors, cards, chips, boards, and modules, it is highly desirable that such connections be separable and reconnectable in the final product.
Pin-type connectors soldered into plated through holes or vias are among the most commonly used in the industry today. Pins on the connector body are inserted through plated holes or vias on a printed circuit board and soldered in place using conventional means. Another connector or a packaged semiconductor device is then inserted and retained by the connector body by mechanical interference or friction. The tin lead alloy solder and associated chemicals used throughout the process of soldering these connectors to the printed circuit board have come under increased scrutiny due to their environmental impact. The plastic housings of these connectors undergo a significant amount of thermal activity during the soldering process, which stresses the component and threatens reliability.
The soldered contacts on the connector body are typically the means of supporting the device being interfaced by the connector and are subject to fatigue, stress deformation, solder bridging, and co-planarity errors, potentially causing premature failure or loss of continuity. In particular, as the mating connector or semiconductor device is inserted and removed from the present connector, the elastic limit on the contacts soldered to the circuit board may be exceeded causing a loss of continuity. These connectors are typically not reliable for more than a few insertions and removals of devices. These devices also have a relatively long electrical length that can degrade system performance, especially for high frequency or low power components. The pitch or separation between adjacent device leads that can be produced using these connectors is also limited due to the risk of shorting.
Another electrical interconnection method is known as wire bonding, which involves the mechanical or thermal compression of a soft metal wire, such as gold, from one circuit to another. Such bonding, however, does not lend itself readily to high density connections because of possible wire breakage and accompanying mechanical difficulties in wire handling.
An alternate electrical interconnection technique involves placement of solder balls or the like between respective circuit elements. The solder is reflowed to form the electrical interconnection. While this technique has proven successful in providing high density interconnections for various structures, this technique does not allow facile separation and subsequent reconnection of the circuit members.
An elastomer having a plurality of conductive paths has also been used as an interconnection device. The conductive elements embedded in the elastomeric sheet provide an electrical connection between two opposing terminals brought into contact with the elastomeric sheet. The elastomeric material that supports the conductive elements compresses during usage to allow some movement of the conductive elements. Such elastomeric connectors require a relatively high force per contact to achieve adequate electrical connection, exacerbating non-planarity between mating surfaces. Location of the conductive elements is generally not controllable. Elastomeric connectors may also exhibit a relatively high electrical resistance through the interconnection between the associated circuit elements. The interconnection with the circuit elements can be sensitive to dust, debris, oxidation, temperature fluctuations, vibration, and other environmental elements that may adversely affect the connection.
The problems associated with connector design are multiplied when multiple integrated circuit devices are packaged together in functional groups. The traditional way is to solder the components to a printed circuit board, flex circuit, or ceramic substrate in either a bare die silicon integrated circuit form or packaged form. Multi-chip modules, ball grids, array packaging, and chip scale packaging have evolved to allow multiple integrated circuit devices to be interconnected in a group.
One of the major issues regarding these technologies is the difficulty in soldering the components, while ensuring that reject conditions do not exist. Many of these devices rely on balls of solder attached to the underside of the integrated circuit device which is then reflown to connect with surface mount pads of the printed circuit board, flex circuit, or ceramic substrate. As discussed above, these joints have not been proven to be extremely reliable nor easy to inspect for defects. The process to remove and repair a damaged or defective device is costly and many times results in unusable electronic components and damage to other components in the functional group.
Multi-chip modules have had slow acceptance in the industry due to the lack of large scale known good die for integrated circuits that have been tested and burned-in at the silicon level. These dies are then mounted to a substrate which interconnect several components. As the number of devices increases, the probability of failure increases dramatically. With the chance of one device failing in some way and effective means of repairing or replacing currently unavailable, yield rates have been low and the manufacturing costs high.
The present invention relates to a solderless electrical connector in which the contact members provide at least two modes of compliance. The first mode of compliance is determined primarily by the resilience of the encapsulating material. The contact members rotates and/or translates within the encapsulating material during the first mode of compliance, although elastic deformation of the contact members may also be factors. The encapsulating material provides a relatively large range of motion at a low force, allowing for the array of contact members to achieve continuity and planarity despite a significant mismatch. Once the encapsulating material between the contact members and a surface of the housing is substantially compressed, further movement is constrained to promote elastic bending of the contact members in the second mode of compliance.
The present multi-mode compliance connector provides a natural coupling and decoupling between devices, the connector housing, and a PCB. Movement of the contact members corrects for lack of co-planarity, provides shock/vibration dampening, and reduces stress at the interface. The housing and contact member geometry and material are designed to primarily to provide the desired deflection mechanism, rather than contact retention. The solderless suspended contact set allows for compression of both contact tips approximately, at same time. The achievable pitch is less than comparable technologies.
The present multi-mode compliance connector leverages existing infrastructure and technology, requiring less capital investment than other technologies. The encapsulation method allows for the use of shielded, controlled impedance contact members or attenuator, rather than just connector members. Since the contact members are accessed from both the top and bottom of the housing, the contact members typically experience less bending than traditional methods that rely on only topside compliance.
The base metal of the contact members substantially defines the second mode of compliance, providing long term connection that resists failure due to fatigue, vibration, temperature fluctuation, and excessive or repeated insertion. The contact members can be independently adjusted to engage with a wide range of circuit members. The present connector also allows the contact members to be arranged with a pitch of less than about 0.4 millimeters and preferably a pitch of less than about 0.2 millimeters without shorting.
The multiple modes of compliance occur in response to various levels of displacement of the contact members, typically resulting from engagement with one or more circuit members. Elastic deformation of the contact members during the first mode of compliance is typically minimal. Once the encapsulating material is substantially compressed, further displacement of the contact members will flex the contact members in a second mode of compliance, resulting in elastic deformation of the contact members and/or the encapsulating material. In some embodiments, there may be some elastomeric material between the contact members and a surface of the housing. Compression of the encapsulating material may occur at a variety of surfaces on the housing, including flat surfaces or pre-defined end stops, either inside or outside of the housing.
The location where the encapsulating material is compressed may define a flexure point or the contact members may flex at a different location. For example, a curved portion of the contact member may engage with the flat side surface of the housing in the second mode of compliance. In another embodiment. at least a portion of the second mode of compliance is determined by a geometry of the first contact member. For example, cut-outs, thin regions or locations of weakness (referred to collectively as flexure locations) of the contact members may be provided to modify the second mode of compliance.
The insertion force at the first circuit interface portion can be different than at the second circuit interface portion. The present electrical connector provides an initial insertion force and a secondary insertion force with the circuit member. The initial insertion force may be less than, greater than, or equal to the secondary insertion force. Additionally, the second mode of compliance at the first circuit interface portion may be less than, greater than, or equal to the second mode of compliance at the second circuit interface portion.
The resilient or semi-resilient contact members can be a piece of a conductive sheet material, a wire, or a combination thereof. For contact members constructed from sheet materials, various cut-outs and contours may be included to facilitate the interface with circuit members and to engineer the modes of compliance. The first circuit interface portion can provide a wiping engagement with the first circuit member.
The first circuit interface portion can have a shape complementary to the shape of the connector on the circuit member. This arrangement increases the stability of the connection and increases the surface area of contact between the contact members and the connector on the circuit member. One embodiment relates to the cup shaped circuit interface portion.
In one embodiment, the connector apparatus is adapted for electrically connecting first and second circuit members. The connector apparatus comprises an electrically insulative connector housing. Resilient contact members having resilient first and second circuit interface portions are positioned generally within the connector housing. The resilient contact members comprise a first compliant member. A resilient, dielectric encapsulating material surrounding a portion of the resilient contact members comprises a second compliant member. The first and second compliant members are capable of providing a first mode of compliance when the contact members are displaced by a circuit member. Displacement of the contact members in the first mode of compliance is limited by the housing. Once further movement of the contact members is constrained, the contact members flex in the second mode of compliance.
At least one support member may be provided for supporting or suspending the array of contact members. In one embodiment, the support member comprises a pivot point around which the contact members rotate. The support member may also comprises a flexible filament capable of permitting translational and/or rotational movement of the contact members.
The circuit members can be a packaged and an unpackaged integrated circuit device, a printed circuit board, a flexible circuit, a bare-die device, an integrated circuit device, an organic or inorganic substrate, a rigid circuit and virtually any other type of electrical component. As used herein, integrated circuit refers to packaged or unpackaged bare silicon integrated circuit devices. The present electrical connector can be used as a die-level test probe, a wafer probe, a printed circuit probe, a connector for a packaged or unpackaged circuit device, a conventional connector, a semiconductor socket, and the like.
The circuit interface portions are capable of engaging with a connector member selected from the group consisting of an edge card, a j-lead device, a flex circuit, a ribbon connector, printed circuit board, a bare die device, a flip chip, a cable, a ball grid array (BGA), a land grid array (LGA), a plastic leaded chip carrier (PLCC), a pin grid array (PGA), a small outline integrated circuit (SOIC), a dual in-line package (DIP), a quad flat package (QFP), a leadless chip carrier (LCC), and a chip scale package (CSP).
In another embodiment, the connector apparatus for electrically connecting first and second circuit members comprises an electrically insulative connector housing adapted for being positioned substantially between the first and second circuit members. Rigid or semi-rigid contact members having first and second circuit interface portions are positioned generally within the connector housing. A first resilient, dielectric encapsulating material comprising a first compliant member surrounds at least a portion of the contact member. The encapsulating material is capable of providing a first mode of compliance when the contact members are displaced by a circuit member. A second resilient material comprising a second compliant member is interposed between the rigid connector member and the housing, whereby the first and second compliant members are capable of providing a second mode of compliance. Elastic deformation of the first resilient encapsulating material comprises the first mode of compliance. Elastic deformation of the first resilient encapsulating material and the second resilient member comprises the second mode of compliance. Engagement of the contact members with the housing typically initiates translational movement of the contact member.
The present invention is also directed to a replaceable chip module for electrically connecting one or more first circuit members to a second circuit member. The replaceable chip module includes a module housing having a plurality of device sites each capable of receiving at least one first circuit member. A first connector according to the present invention is located in each of the device sites. A second connector is provided for electrically connecting the first connector to the second circuit member.
In one embodiment, the replaceable chip module includes a second connector comprises a second contact members having substantially the same structure as the first contact member. In one embodiment, the first contact members and a second contact members comprise a single contact member extending between the first and second circuit members. A third electrical connector can optionally be provided for electrically connecting the replaceable chip module to a third circuit member. In one embodiment, the third circuit member comprises the present replaceable chip module.
Each of the first circuit members can be removed and replaced in the event of failure, upgraded, or changed in configuration. The short electrical length of the multi-mode compliance connector allows for excellent signal integrity and overall size similar to current packaging techniques. By eliminating the need to solder the first circuit members into the module, the present invention greatly reduces the implications of known good die or burn-in packaged integrated circuits.
In theory, any printed circuit board, multi-chip module, or flex circuit that has components soldered in some arrangement can be eliminated by use of the present replaceable chip module. The present replaceable chip module can replace a printed circuit board with a group of integrated circuit devices soldered thereto. The present invention allows for economical use of conventional materials that do not need to withstand the temperature effects of repeated soldering and reflow. By including locations for many devices in one module, the space required is much smaller than if multiple device connectors were to be used.
The present invention is also directed to a method of utilizing the present replaceable chip module during multiple phases in the life of an integrated circuit device. After placement into the replaceable chip module, the integrated circuit devices can be tested, identified, burned-in, and used in production without ever having to be removed or handled. If one or more of the integrated circuit devices fails during the testing, identification, burn-in, or production phases, the individual circuit device can be removed from the replaceable chip module without damage to the other integrated circuit devices or the replaceable chip module.
In one embodiment, one or more flexible circuits with a matching input/output (I/O) pattern is located at the interface of one of the circuit members with the present solderless electrical connector. The flexible circuit member contains an array of contact pads that mate with the first circuit interface portions of the contact members and the pads on the printed circuit board. The flexible circuit permits individual pins on the integrated circuit device to be probed during normal operation.